Generally component parts of assemblies are manufactured within acceptable levels of dimensional tolerance. Where components are made from a laid up or moulded fibre composite material it is common to have one surface which is tightly dimensionally controlled while the other surface is not so controlled. When such component parts are assembled together into a multi-part structural assembly, such as an aircraft wing, small clashes (interference fits) or gaps (clearance fits) can result. In the event of an interference fit some material must be removed whilst still retaining the structural integrity of the assembly. For a minimum weight optimised design that cannot be done unless additional material was included in the design for such a purpose. That can result in surplus material remaining part of the finished assembly when material removal is not required. For clearance fits, various options are available for filling the gap including liquid shimming and the insertion of a hard packer. As the thickness of the packer increases, there is an increasing likelihood that the structural integrity of the assembled component will be compromised as the joint will relax over time due to fatigue cycling and material creep, reducing the packer's shear transmission capability. Moreover, the use of packers adds weight to the final assembly which may be unnecessary.